The present invention relates to flash assemblies and particularly to assemblies utilizing high voltage, arc discharge flash tubes. The invention more particularly relates to such assemblies wherein the flash tube is externally triggered.
Flashtubes generally comprise two spaced apart electrodes within a sealed glass envelope having a rare gas fill, typically xenon, at a sub-atmospheric pressure. Such lamps are connected across a large capacitor charged to a substantial potential which is, however, insufficient to ionize the xenon fill gas. Upon application of an additional pulse of sufficient voltage, the xenon is ionized and an electric arc is formed between the two electrodes, resulting in a discharge of the large capacitor through the flash tube and emission of a short burst of intense light. In many external triggering situations, the pulse voltage is applied between a trigger wire wrapped around the tube's envelope and the electrodes extending within the envelope. Usually, this form of external triggering also requires placement of a thin conductive film (e.g. tin oxide) to encompass the lamp's envelope and internally positioned electrodes. The described trigger wire is thereafter wrapped around the envelope in electrical contact with the film. The conductive film serves as a vehicle for uniformly distributing the energy from the respective high power source to effect the desired ionization. Understandably, the requirements for this film and the precisioned wrapping of the trigger wire thereabout increase the manufacturing costs of the assembly.
In recent years, it has become desirable in the photographic industry to employ the aforementioned arc discharge flash tubes within various camera assemblies. These components receive the required triggering energy from a power source located within the camera or a power pack attached thereto. The highly intense discharge from the flash tube is synchronized with the shutter mechanism of the camera to assure sufficient light when the shutter is opened.
The flash assembly of the instant invention eliminates the need for the aforedescribed conductive film and externally wrapped trigger wire. Accordingly, the present invention is more easily assembled, less expensive to manufacture, and substantially less difficult to repair or replace than known electrical flash assemblies of the prior art.
It is believed therefore that a flash assembly having the several advantageous features described above would constitute an advancement in the art.